Mechanical working in the presence of a metal containing copper or aluminum

ABSTRACT

The present invention is directed to a method for mechanical working of a metal containing copper, aluminum or an alloy thereof. The method is carried out in the presence of an aqueous cooling lubricant containing an alkanol amine. The lubricant is capable of preventing and reducing the corrosion of both metals and iron.

This application is the national phase under 35 U.S.C. §371 of PCTInternational Application No. PCT/SE99/01521 which has an Internationalfiling date of Sep. 3, 1999, which designated the United States ofAmerica.

The present invention relates to a method for mechanical working of ametal containing copper, aluminum or an alloy thereof The method iscarried out in the presence of an aqueous cooling lubricant containingan alkanol amine. Preferably the alkanol amine is used in combinationwith a phosphate ester or a carboxylic acid. The lubricant is capable ofreducing or preventing the corrosion of both metals as well as iron. Inaddition it also contributes in an essential way to the lubrication.

Aluminum and copper and alloys of these metals are among the most commonconstruction metals. The mechanical working is usually performed in thepresence of an aqueous cooling lubricant. A disadvantage of many aqueouscooling lubricants is that they frequently contain an iron corrosioninhibitor, such as monoethanolamine, diethanolamine or triethanolamine,which has a detrimental effect on copper, aluminum or alloys thereof andcauses discoloration and dissolution. Beside the corrosion, anydissolved metal also constitutes an environmental hazard and isdifficult to remove from water in the process of disposal of the coolinglubricant.

In order to mitigate the negative effects of alkanol amine, anionicsurface active components with long aliphatic groups, such as groupswith 14-44 carbon atoms have been used. Exemplary components arephosphate esters and fatty acids and dimer acids. Their protectiveaction depends on the formation of insoluble, organic layers on themetal surfaces. If, however, dissolved di- or trivalent metals exist inthe cooling lubricant, the anionic components will form insoluble saltswith these metals ions. This may sometimes further increase thecorrosion inhibiting effect, but it will also lead to the formation ofan undesirable sticky precipitation, which e.g. tend to interfere withthe cleaning of the cooling lubricant. Another drawback is thedifficulty to remove the hydrophobic layers formed on the metalsurfaces. If they are not removed, they will cause problems in thesubsequent surface treatment, for example pickling, phosphatizing,galvanizing or other metal depositing processes. The presence of thelong chain anionic components may also cause undesirable foaming andscum.

U.S. Pat. No. 4,315,889 discloses a method of reducing the release ofcobalt by performing the metal working in the presence of a coolinglubricant containing, as an active component, a specific triazole orthiadiazole compound. However, since these active compounds are consumedin the presence of ethanolamines, the aqueous cooling lubricant has tobe regularly upgraded.

EP-A-0180561 describes the use of a tertiary alkanol amine compound forreducing the release of cobalt. According to the application thetertiary alkanol amine compound can advantageously be combined withcarboxylic acids for further protection against the release of cobaltand the corrosion of iron.

According to the present invention it has now been found possible toreduce or eliminate the above mentioned problems by using certainalkanol amines, which do not dissolve or discolor copper or aluminummetals. In more detail, the present invention relates to a process forthe mechanical working of metals containing copper, aluminum or alloysthereof, which process is performed in the presence of an aqueouscooling lubricant having a pH of 6-10 and containing an alkanol amine ofthe formula

N(R₃)(R₄)(R₅)  (I),

where R₃, R₄ and R₅ independently of each other designate a group(AO)_(n)H, where AO is an ethyleneoxy group or a propyleneoxy group andn is a number from 2-6, and the number of ethyleneoxy groups in relationto the number of propyleneoxy groups is between 2:1 and 1:3.

Particular effective in avoiding the side effects of conventional ironcorrosion inhibiting components in earlier used formulations areaccording to the invention aqueous cooling lubricants in which thealkanol amine I are supplemented by a short chain anionic compoundselected from the group consisting of

a phosphate ester of the formula

R₁(oxyalkylene)_(n)OP(O)(X)(OH)  (II), or

(HO)₂(O)P-(oxyalkylene)_(m)-OP(O)(OH)₂  (III),

 where R₁ is an alkyl group with 1-12 carbon atoms. X is hydroxyl or thegroup R₁O, where R₁ has the above mention meaning, oxyalkylene is agroup containing 2-4 carbon atoms, n is a number from 1-15 and m is anumber from 4-20, or a salt thereof, or

a carboxylic acid of the formula

R₂(COOH)_(p)  (IV),

 where R₂ is an alkyl group with 4-10 carbon atoms and p is 1 or 2, or asalt thereof, or a mixture of any of the anionic compounds III II andIV. The total amount of the anionic compounds II, III and IV is normally10-1000%, preferably 15-300% by weight of the alkanol amine I. Thealkanol amine I, preferably in combination with at least one of theanionic compounds II, III and IV, results in an essential reduction inthe amount of dissolved copper and discolored copper and aluminum incomparison with a corrosion inhibitor consisting of a carboxylic acidand an alkanol amine, such as triethanolamine. The compounds I, II, IIIand IV also contribute to the lubrication.

The alkanol amine I contains always at least 2 propyleneoxy groups.Preferably the alkanol amines are produced by ethoxylation of ammoniawith 2-4 moles ethylene oxide followed by propoxylation with 4-7 molesper mole ammonia. The hydroxyl groups of these alkanol amines willconsist of only secondary hydroxyl groups. The ratio of ethyleneoxygroups to propyleneoxy groups is preferably between 1:1 and 1:3.

The carboxylic acid of formula IV contains an aliphatic group which canbe saturated or unsaturated, straight or branched. Preferably thealiphatic group of monocarboxylic acids contains 5-9 carbon atoms, whilethe dicarboxylic acids preferably have an aliphatic group with 6-10carbon atoms. Suitable examples of carboxylic acids are azelaic acid,pelargonic acid, sebacic acid, isononanoic acid, neodecanoic acid,n-octanoic acid, n-decanoic acid and dodecandioic acid. The carboxylicacids having a branched aliphatic group of the preferred size are oftenutilized, since they are low foaming.

In the phosphate esters of formulae II and III, the (oxyalkylene)_(n)group and (oxyalkylene)_(m) group respectively, are suitable selected insuch a way that the esters will be water-soluble or easily dispersiblein water. The aliphatic group R₁ can be saturated or unsaturated,straight or branched and contains preferably 2-8 carbon atoms.Preferably the phosphate ester with formula II consists of at least 50%by weight of monoesters. In formula III the polyoxyalkylene chainpreferably consists, at least partially, of oxyalkylene groups with 3-4carbons atoms and m preferably is at least 6, since these diphosphateesters beside the corrosion inhibiting effect give a considerablecontribution to the lubrication Especially suitable are thosediphosphate esters, which contains a polyoxypropypene chain with 5-10oxypropylene units.

The content of the alkanol amine I and the anionic compounds II, III andIV may vary within wide limits, but is normally between 0.1 and 10% byweight, preferably between 1 and 7% by weight of the cooling lubricantready for use. The cooling lubricant can also contain a number of otheradditives, such as additional corrosion-inhibiting additives andlubricants, pH-regulating or controlling additives, bactericidal agents,viscosity-increasing additives, solubilizers, perfumes, colourants etc.

Examples of suitable additional corrosion inhibitors are aminescompounds, such as triazole and thiadiazole compounds, and inorganiccompounds, such as alkali metal hydroxides and boric acid, and reactionproducts between boric acid and/or carboxylic acids with organiccompounds, such as alkanol amines. The content of these additionalcorrosion inhibitors may be up to 3% by weight of the cooling lubricant.

Although the cooling lubricant containing the alkanolamine I and theanionic surfactants II, III and IV has an adequate lubrication abilityfor most applications it may be occasions where improved lubrication isdesired. Examples of suitable lubricants to be incorporated into acooling lubricant according to the invention are those selected from thegroup consisting of esters or amides of mono- or dicarboxylic acidshaving at least 12 carbon atoms in the acyl groups, aliphatic phosphateesters containing one or two aliphatic groups with 6-18 carbon atoms,nonionic alkylene oxide adducts with a molecular weight above 400, suchas polypropylene glycols, glycols of randomly distributed propyleneoxyand ethyleneoxy groups and block polymers of propylene oxide andethylene oxide, and mixtures thereof The content of these additionallubricants may be up to 3% by weight of the cooling lubricant ready foruse.

The solubilizers are usually low molecular compounds containing at leastone hydroxyl. The molecular weight is normally below 400. Examples ofsuitable solubilizers are propypeneglycol, ethylene diethyleneglycol,butyl diethyleneglycol and butyl triethyleneglycol.

When preparing a cooling lubricant according to the invention, it issuitable to first prepare a concentrate, for example by first mixing thealkanol amine I, anionic compounds II, III and IV and water, and thenthe supplementary ingredients. The amount of water is suitably between5-80% by weight of the concentrate. A typical concentrate according tothe invention has the following composition:

alkanol amine I 20-95, preferably 50-90% by weight anionic compounds II,III and IV 0-60, preferably 10-50% by weight additional corrosioninhibitors 0-30, preferably 0-15% by weight additional lubricants 0-30,preferably 0-15% by weight water 5-80, preferably 10-50% by weight otheringredients 0-30, preferably 0-15% by weight

The total amount of the additional corrosions inhibitors and lubricantsand other ingredients is often 5-40% by weight of the concentrate.Before the concentrate is used, it is diluted with water so that thecooling lubricant ready for use will have a total content of 0.5-20% byweight, preferably 2-10% by weight.

The present invention is further illustrated by the following Examples.

EXAMPLE 1

Cooling lubricants ready for use were prepared from the aqueousconcentrates in the Table 1 below. The content of water was 30% byweight. The pH of the concentrates was adjusted to 9 by adding KOHbefore they were diluted with water to an active content of 4% byweight. The corrosion inhibiting effects on copper and iron of thesefluids were determined at an ambient temperature of 22° C. by thefollowing test methods.

Fe-corrosion tests were done by placing 30 grams of cast iron chipsevenly spread on a circular filter paper with a diameter of 90 mm. 1.25gram of one of the cooling lubricants was dispensed at the center of thefilter paper, which was placed in a plastic Petri dish and covered by alid. The corrosion taken place after 24 hours was determined by visuallyinspection of the rust staining according to a scale, where 0=nocorrosion, 1=one stain, 2=two or three stains, 3=more than three stainsup to 10% of the paper surface discolored, 4=between 10 and 25% of thepaper surface discolored, and 5=more than 25% of the paper surfacediscolored.

Cu-corrosion tests were performed by assessing the amount of leachedcopper obtained, when a 20 ml glass vial containing 5 glass beads, 5 mgof fine powder of copper and 10 ml of one of the fluids was shaken for 7days. The amount of copper dissolved was measured by use of an atomicabsorption spectrophotometer (AAS). Initial screening of the fluids wasdone by using analytical sticks from Merck and only samples, which werefound to contain less than 30 ppm of copper, were subjected to AASanalysis.

The results obtained from the corrosion tests are shown in Table 2.

TABLE 1 Aqueous concentrates Components % by weight I II III IV V VI VIIVIII Composition 20 — — — 50 — — — 1 2 20 — — — — 50 — — 3 20 — — — — —50 — 4 20 — — — — — — 50 5 — 20 — — 50 — — — 6 — 20 — — — 50 — — 7 — 20— — — — 50 — 8 — 20 — — — — — 50 9 — — 20 — 50 — — — 10 — — 20 — — 50 —— 11 — — 20 — — — 50 — 12 — — 20 — — — — 50 13 — — — 20 50 — — — 14 — —— 20 — 50 — — 15 — — — 20 — — 50 — 16 — — — 20 — — — 50 17 10 — 10 — 50— — — 18 10 — 10 — — 50 — — 19 10 — 10 — — — 50 — 20 10 — 10 — — — — 5021 10 — — 10 50 — — — 22 10 — — 10 — 50 — — 23 10 — — 10 — — 50 — 24 10— — 10 — — — 50 25 — 10 10 — 50 — — — 26 — 10 10 — — 50 — — 27 — 10 10 —— — 50 — 28 — 10 10 — — — — 50 29 — 10 — 10 50 — — — 30 — 10 — 10 — 50 —— 31 — 10 — 10 — — 50 — 32 — 10 — 10 — — — 50

Component I=phosphate ester, where R₁=hexyl, oxyalkylene=oxyethylene,n=5, X=hydroxyl,

Component II=diphosphate, where oxyalkylene=oxypropylene, m=9,

Component III=isononanoic acid,

Component IV=neodecanoic acid,

Component V=triethanolamine

Component VI=triethanolamine+4 propylene oxide,

Component VII=triethanolamine+5 propylene oxide, and

Component VIII=triethanolamine+6 propylene oxide

TABLE 2 Corrosion test results Composition 1 2 3 4 5 6 7 8 Fe-corrosion0 0 1 3 0 0 2 3 Cu-corrosion ppm 350 20 20 10 350 30 30 10 Composition 910 11 12 13 14 15 16 Fe-corrosion 0 0 1 0 0 1 1 2 Cu-corrosion ppm 35050 50 15 350 30 20 10 Composition 17 18 19 20 21 22 23 24 Fe-corrosion 00 1 0 0 0 0 1 Cu-corrosion ppm 350 20 10 5 350 10 10 10 Composition 2526 27 28 29 30 31 32 Fe-corrosion 0 0 0 1 0 0 0 0 Cu-corrosion ppm 35020 10 5 350 10 5 5

From the results it is evident that the metal working fluids formulatedaccording to the invention, namely compositions 2-4, 6-8, 10-12, 14-16,18-20, 22-24, 26-28 and 30-32 have excellent corrosion inhibitingproperties as regards copper and are superior to the comparison fluids1, 5, 9, 13, 17, 21, 25 and 29. The iron corrosion inhibiting propertiesof the formulations according to the invention are acceptable and in alltests zero iron corrosion were obtained, when the concentration of theactive components was raised to 5,5% by weight.

EXAMPLE 2

Since brass and aluminum are often used in applications where visualappearance is important an immersion test was performed to show thedegree of discoloration caused by the test solutions. Strips of 5 mmwidth and 60 mm length of each metal were placed in separate glass vialsand tests solutions were added to cover half the length of the uprightstanding strips. The corrosion was visually determined after 7 days. Thediscoloration of the strips was measured according to a scale from 0 to5, where 0 represent no corrosion, 1 indicate that up to 5% of thesurface is black, 2 that 5-10% of the surface is black, 3 that 10-25% ofthe surface is black, 4 that 25-90% of the surface is black, and 5 that90-100% of the surface is black. For the brass strips it was also notedif the test solutions were colored blue.

The following results were obtained. The compositions with their numberscorresponds to the compositions in Example 1.

TABLE 3 Composition no 1 4 5 8 9 12 Brass -corrosion degree 5 0 5 0 5 1-solution blue — blue — blue — Aluminum 5 0 5 0 5 0 Composition no 13 1620 24 28 32 Brass -corrosion degree 5 2 1 1 0 1 -solution blue light —light blue — light blue blue Aluminum 5 0 0 0 0 0

From the results it is evident that the solution according to theinvention are superior to the comparison solutions based ontriethanolamine.

What is claimed is:
 1. A method for mechanically working of a metalcontaining copper, aluminum or an alloy thereof comprising the use of anaqueous cooling lubricant having a pH between 6 and 10 and containing analkanol amine of the formula N(R₃)(R₄)(R₅)  (I), where R₃, R₄ and R₅independently of each other designate a group (AO)_(n)H, where AO is anethyleneoxy group or a propyleneoxy group and n is a number from 2-6,the number of ethyleneoxy groups in relation to the number ofpropyleneoxy groups is between 2:1 and 1:3.
 2. A method according toclaim 1, wherein the alkanol amine I has three secondary hydroxylgroups.
 3. A method according to claim 2, wherein the alkanol amine isobtained by ethoxylation of 1 mole ammonia with 2-4 moles ethylene oxidefollowed by propoxylation with 4-7 moles propylene oxide.
 4. The methodaccording to claim 1, wherein the lubricant also contains an anioniccompound selected from the group consisting of a phosphate ester of theformula R₁(oxyalkylene)_(n)OP(O)(X)(OH)  (II), or(HO)₂(O)P-(oxyalkylene)m-OP(O)(OH)₂  (III), where R₁ is an alkyl groupwith 1-12 carbon atoms, X is hydroxyl or the group R₁O, where R₁ has theabove mentioned meaning, oxyalklene is a group containing 2-4 carbonatoms, n is a number form 1-15 and m is a number from 4-20, or a saltthereof, or a carboxylic acid of the formula R₂(COOH)_(p)  (IV), whereR₂ is an alkyl group with 6-12 carbon atoms and p is 1 or 2, or a saltthereof, or a mixture thereof.
 5. A method according to claim 4, whereinthe phosphate ester III contains a polyoxyalkylene chain, which at leastpartially consists of oxyalkylene groups with 3-4 carbon atoms, and thephosphate ester II consists of at least 50% by weight of monoesters. 6.A method according to claim 3, wherein that the carboxylic acid offormula IV is a monocarboxylic acid, where R₂ is a branched aliphaticgroup with 5-9 carbon atoms or a dicarboxylic acid, where R₂ is abranched aliphatic group with 6-10 carbon atoms.
 7. A method accordingto claim 4, wherein the cooling lubricant contains at least onephosphate ester of formula II or III and a carboxylic acid of formulaIV.
 8. The method of claim 4, wherein the phosphate ester has theformula III.
 9. An aqueous lubricant composition having a pH between 6and 10 which comprises: an alkanol amine of the formulaN(R₃)(R₄)(R₅)  (I),  wherein R₃, R₄ and R₅ independently of each otherdesignated a group (AO)_(n)H, where AO is an ethyleneoxy group or apropyleneoxy group and n is a number from 2-6, the number of ethyleneoxygroups in relation to the number of propyleneoxy group is between 2:1and 1:3; an anionic compound selected from the group consisting of aphosphate ester of the formula  R₁(oxyalkylene)_(n)OP(O)(X)(OH)  (II),or (HO)₂(O)P-(oxyalkylene)m-OP(O)(OH)₂  (III),  where R₁ is an alkylgroup with 1-12 carbon atoms, X is hydroxyl or the group R₁O, where R₁is an alkyl group with 1-12 carbon atoms, oxyalklene is a groupcontaining 2-4 carbon atoms, n is a number from 1-15 and m is a numberfrom 4-20, or a salt thereof; and a carboxylic acid of the formulaR₂(COOH)_(p)  (IV),  where R₂ is an alkyl group with 6-12 carbon atomsand p is 1 or 2, or a salt thereof, or a mixture thereof; wherein thealkanol amine I is present in an amount of 50-90% by weight, the anioniccompounds II, III and IV are present in an amount of 10-50% by weight,with the substantial balance being water.
 10. The composition accordingto claim 9, wherein the total amount of additional corrosion inhibitors,additional lubricants and other ingredients is 5-40% by weight.
 11. Thecomposition according to claim 9, wherein the water is present in anamount of 10-50% by weight.
 12. The composition according to claim 10,wherein the additional corrosion inhibitors are present in an amount of0-15% by weight and the additional lubricants are present in an amountof 0-15% by weight.
 13. The aqueous lubricant composition of claim 9,wherein the phosphate ester has the formula III.
 14. The aqueouslubricant composition of claim 9, for mechanically working a metalcontaining copper, aluminum or alloys thereof.
 15. The aqueous lubricantcomposition of claim 9, wherein the phosphate ester has the formula III.